(a) Field of the Invention
The present invention relates to a battery assembly. More particularly, the present invention relates to a battery assembly mounted on a hybrid electric vehicle that prevents a thermal runaway caused by overcharging.
(b) Description of the Related Art
In general, a high voltage battery is used in a hybrid electric vehicle or an electric vehicle as a power source. The high voltage battery is mounted on a vehicle in a form of one pack by connecting about 50 to 100 cells in series according to a necessary capacity of the battery. When the battery cell is overcharged, swelling of the battery cell occurs due to the internal temperature of the battery cell increasing and a pore of a separator disposed between a positive electrode and a negative electrode of the battery cell closes. The internal temperature of the battery cell then continues to increase causing thermal runaway. Consequently, the hybrid electric vehicle having the battery pack may incur a safety problem.
Particularly, the hybrid electric vehicle should prevent overcharging of the battery when an amount of regenerative braking of greater than a battery capacity is generated from a motor. According to a conventional art, the battery can prevent overcharging by breaking a lead tab when the swelling of the battery cell occurs. However, the lead tab is thickened when the battery cell has a substantially high capacity, thus causing a problem with breaking the lead tab of the battery cell. When the lead tab is not broken, the thermal runaway occurs according to a chemical reaction within the battery cell.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.